1. Field of the Invention
The present invention relates to an air-fuel ratio control apparatus of an internal combustion engine.
2. Description of the Related Art
According to Japanese Patent No. 3404872 (U.S. Pat. No. 5,529,047), for example, when the learning completion conditions of learning an air-fuel ratio are not satisfied for a certain period, the learning of the air-fuel ratio is temporarily stopped and purge is forcibly performed. With this, when purge is stopped for a long time, it is prevented that because the quantity of adsorption of a canister reaches a saturated state, the adsorption becomes impossible from that time.
In the foregoing conventional technology, when purge is performed while the air-fuel ratio is being learned, it is impossible to discriminate whether a deviation between the air-fuel ratio detected by an air-fuel sensor or the like and a target air-fuel ratio is caused by performing the purge or by the other factor (for example, individual difference of an injector or the like), so the learning of the air-fuel ratio is temporarily stopped and purge is forcibly performed.
However, if it is possible to discriminate whether the foregoing deviation is caused by performing the purge or by the other factor, the purge can be performed while the learning of the air-fuel ratio is not temporarily stopped. In other words, the learning of the air-fuel ratio and the purge can be performed at the same time.